Typical audio speakers use a vibrating diaphragm to produce soundwaves. The diaphragm is usually connected to a voice coil (i.e., an electromagnet). The voice coil is placed within the magnetic field of a permanent magnet. When an analog electrical signal is applied to the voice coil, the voice coil is either attracted to or repulse by the permanent magnet, depending on the polarity of the analog electrical signal. The analog electrical signal's alternating polarity imparts motion to the attached diaphragm, thus creating a soundwave. By varying the strength and the time it takes the analog electrical signal to change polarity, the volume and frequency, respectively, of the soundwave produced is regulated.
Most of today's sound recordings (for example, music, movies, etc.) are digitally recorded on, for example, CD's, DVD's, etc. Typical audio speakers, however, require that the digital sound recording be converted into an analog signal to drive the audio speaker's voice coil. Thus, additional digital-to-analog circuitry must be provided in the driver device (e.g., CD player, DVD player, etc.). The additional circuitry increases the complexity, size, cost, and power consumption of the driver device.
Thus, a need exists for a method and apparatus for directly reconstructing sound with a digital signal (i.e., without the need for converting the digital signal to an analog signal).